A conventional battery charging system for a battery-operable device typically includes an alternating current (AC) adapter input port, a power conversion charger for converting AC power to direct current (DC) power, a filter capacitor, a battery, and a charging current path, which can include a resistor, a battery switch, and one or more associated cables. For example, the battery-operable device can be a laptop computer, a tablet computer, a smartphone, a medical device, an industrial device, etc. In the conventional battery charging system, the power conversion charger can deliver DC power for charging the battery, as well as operating main computer or processor system components (the “main system components”) within the battery-operable device. The operation of the main system components is typically separate from the function of charging the battery. For example, the charging of the battery can take place while the main system components are either operating or shutdown. Further, the main system components can operate both while the charging of the battery is in progress and after the charging of the battery has completed, as well as while the battery is removed or otherwise absent from the battery-operable device.
The conventional battery charging system described herein has several drawbacks, however. For example, the conventional battery charging system typically only controls and/or regulates an output voltage of the battery charging system at a common node of the main system components and the filter capacitor, and does not generally control/regulate the voltage of the battery itself. Further, the voltage drop across the charging current path, which can include the resistor, the battery switch, and the associated cable(s), can significantly impact the voltage of the battery, resulting in reduced accuracy of the battery voltage, increased battery charging time, and/or reduced battery capacity.
Moreover, the power conversion charger generally includes power switches (e.g., metal oxide semiconductor field effect transistor (MOSFET) switches) that implement a typical pulse width modulation (PWM) switching scheme, which can result in power losses proportional to the size and/or switching frequency of the respective power switches. Further, while the power conversion charger operates in a low output current mode, such as a system standby mode, the power switches can continue to operate within the typical PWM switching scheme, causing unwanted power consumption and/or power dissipation inside the power conversion charger. Although the level of such unwanted power consumption/dissipation is typically low, it can cause a significant amount of energy to accumulate in situations where the power conversion charger operates in the system standby mode for an extended period of time. Such unwanted power consumption/dissipation can also cause reduced power efficiency under light load conditions, possibly preventing the battery-operable device from meeting certain international standards for energy efficient consumer products, such as the Energy Star™ standards.
It would therefore be desirable to have improved systems and methods of charging battery power that can avoid at least some of the drawbacks of conventional battery charging systems.